The present invention relates to a display apparatus including organic electroluminescence devices each of which comprises an organic light emission layer, and a method of manufacturing the same.
An organic electroluminescence device utilizing electroluminescence (hereinafter referred to as EL) of an organic material comprises an organic layer composed of a lamination of an organic hole transport layer and an organic light emission layer between a lower electrode and an upper electrode, and has drawn attention as a light emitting device capable of high-luminance light emission when driven by a low-voltage DC current.
An active matrix type display apparatus using such organic EL devices (namely, an organic EL display) comprises thin film transistors arranged at each pixel on a substrate. The organic EL devices are formed on an inter-layer insulating film provided so as to cover the thin film transistors. The organic EL device is comprised of a lower electrode patterned on the basis of each pixel in the state of being connected to the thin film transistor, an insulating film surrounding a central portion of the lower electrode while exposing the central portion as a pixel opening, an organic layer provided on the lower electrode in the pixel opening which is separated by the insulating film, and an upper electrode provided in the state of covering the organic layer. Of these components, the upper electrode is formed for example as a solid-printed-like film covering a plurality of pixels, and is used as an upper common electrode between the plurality of pixels.
In the active matrix type display apparatus, in order to secure the numerical aperture of the organic EL devices, it is effective to configure the display apparatus as the so-called top emission type structure in which light is taken out on the side opposite to the substrate. Therefore, the upper electrode is required to be thinned for securing a light-transmitting property, which tends to raise resistance value, thereby easily causing a voltage drop.
In view of this problem, there has been proposed a structure in which an auxiliary wiring formed of a highly conductive metallic material is formed on the insulating film between the pixel openings, and the upper electrode is connected to the auxiliary electrode, thereby preventing the voltage drop in the upper electrode. The auxiliary wiring may be formed as a part of a member constituting a rib on the insulating film covering the portion between the pixel openings, as shown for example in Patent Reference 1 given below. The rib is a portion on which a vapor deposition mask is mounted in the step of vapor depositing the organic layer after the formation of the insulating film (see Patent Reference 1). Also, there has been proposed a configuration in which the auxiliary wiring is composed of the same layer as that of the lower electrodes, and the organic layer is independently formed on each of the lower electrodes (see Patent Reference 2 given below).
Patent Reference 1: Japanese Patent Laid-open No. 2001-195008 (page 4 and FIG. 1)
Patent Reference 2: Japanese Patent Laid-open No. 2002-318556
In the display apparatus having the auxiliary wiring in the configuration shown in Patent Reference 1, however, a special layer for forming the auxiliary wiring is provided, leading to a complication of the layer structure in the display apparatus. Besides, a special step for forming the auxiliary wiring is needed, causing an increase in the number of steps for manufacturing the display apparatus.
The complication of the layer structure and the increase in the number of manufacturing steps cause increases in the product cost and manufacturing cost of the display apparatus, and cause a lowering in yield due to a trouble peculiar to the increased number of manufacturing steps.
In addition, in the configuration in which the auxiliary wiring is composed of the same layer as that of the lower electrodes as shown in Patent Reference 2, the organic layer is independently formed on the lower electrodes, and it is necessary to enlarge the spacing between the pixel openings so that the adjacent organic layers do not overlap on each other. This hinders enhancement of the degree of integration of pixels and enhancement of fineness of display performance.